Add very initial RESUME cap and command

irc/capability.go

 var (
 	// SupportedCapabilities are the caps we advertise.
 	// MaxLine, SASL and STS are set during server startup.
-	SupportedCapabilities = caps.NewSet(caps.AccountTag, caps.AccountNotify, caps.AwayNotify, caps.CapNotify, caps.ChgHost, caps.EchoMessage, caps.ExtendedJoin, caps.InviteNotify, caps.Languages, caps.MessageTags, caps.MultiPrefix, caps.Rename, caps.ServerTime, caps.UserhostInNames)
+	SupportedCapabilities = caps.NewSet(caps.AccountTag, caps.AccountNotify, caps.AwayNotify, caps.CapNotify, caps.ChgHost, caps.EchoMessage, caps.ExtendedJoin, caps.InviteNotify, caps.Languages, caps.MessageTags, caps.MultiPrefix, caps.Rename, caps.Resume, caps.ServerTime, caps.UserhostInNames)
 
 	// CapValues are the actual values we advertise to v3.2 clients.
 	// actual values are set during server startup.

irc/caps/constants.go

 	MultiPrefix Capability = "multi-prefix"
 	// Rename is this proposed capability: https://github.com/SaberUK/ircv3-specifications/blob/rename/extensions/rename.md
 	Rename Capability = "draft/rename"
+	// Resume is this proposed capability: https://github.com/DanielOaks/ircv3-specifications/blob/master+resume/extensions/resume.md
+	Resume Capability = "draft/resume"
 	// SASL is this IRCv3 capability: http://ircv3.net/specs/extensions/sasl-3.2.html
 	SASL Capability = "sasl"
 	// ServerTime is this IRCv3 capability: http://ircv3.net/specs/extensions/server-time-3.2.html

irc/client.go

 	rawHostname        string
 	realname           string
 	registered         bool
+	resumeDetails      *ResumeDetails
 	saslInProgress     bool
 	saslMechanism      string
 	saslValue          string
 		return
 	}
 
+	// apply resume details if we're able to.
+	client.TryResume()
+
+	// finish registration
 	client.Touch()
 	client.updateNickMask("")
 	client.server.monitorManager.AlertAbout(client, true)
 }
 
+// TryResume tries to resume if the client asked us to.
+func (client *Client) TryResume() {
+	if client.resumeDetails == nil {
+		return
+	}
+
+	server := client.server
+
+	// just grab these mutexes for safety. later we can work out whether we can grab+release them earlier
+	server.clients.Lock()
+	defer server.clients.Unlock()
+	server.channels.Lock()
+	defer server.channels.Unlock()
+
+	oldnick := client.resumeDetails.OldNick
+	timestamp := client.resumeDetails.Timestamp
+	var timestampString string
+	if timestamp != nil {
+		timestampString := timestamp.UTC().Format("2006-01-02T15:04:05.999Z")
+	}
+
+	oldClient := server.clients.Get(oldnick)
+	if oldClient == nil {
+		client.Send(nil, server.name, ERR_CANNOT_RESUME, oldnick, "Cannot resume connection, old client not found")
+		return
+	}
+
+	oldAccountName := oldClient.AccountName()
+	newAccountName := client.AccountName()
+
+	if oldAccountName == "" || newAccountName == "" || oldAccountName != newAccountName {
+		client.Send(nil, server.name, ERR_CANNOT_RESUME, oldnick, "Cannot resume connection, old and new clients must be logged into the same account")
+		return
+	}
+
+	if !oldClient.HasMode(TLS) || !client.HasMode(TLS) {
+		client.Send(nil, server.name, ERR_CANNOT_RESUME, oldnick, "Cannot resume connection, old and new clients must have TLS")
+		return
+	}
+
+	// send RESUMED to the reconnecting client
+	if timestamp == nil {
+		client.Send(nil, oldClient.NickMaskString(), "RESUMED", oldClient.nick, client.username, client.Hostname())
+	} else {
+		client.Send(nil, oldClient.NickMaskString(), "RESUMED", oldClient.nick, client.username, client.Hostname(), timestampString)
+	}
+
+	// send QUIT/RESUMED to friends
+	for friend := range oldClient.Friends() {
+		if friend.capabilities.Has(caps.Resume) {
+			if timestamp == nil {
+				friend.Send(nil, oldClient.NickMaskString(), "RESUMED", oldClient.nick, client.username, client.Hostname())
+			} else {
+				friend.Send(nil, oldClient.NickMaskString(), "RESUMED", oldClient.nick, client.username, client.Hostname(), timestampString)
+			}
+		} else {
+			friend.Send(nil, oldClient.NickMaskString(), "QUIT", "Client reconnected")
+		}
+	}
+
+	// apply old client's details to new client
+	client.nick = oldClient.nick
+
+	for channel := range oldClient.channels {
+		channel.stateMutex.Lock()
+
+		oldModeSet := channel.members[oldClient]
+		channel.members.Remove(oldClient)
+		channel.members[client] = oldModeSet
+		channel.regenerateMembersCache()
+
+		// send join for old clients
+		for member := range channel.members {
+			if member.capabilities.Has(caps.Resume) {
+				continue
+			}
+
+			if member.capabilities.Has(caps.ExtendedJoin) {
+				member.Send(nil, client.nickMaskString, "JOIN", channel.name, client.account.Name, client.realname)
+			} else {
+				member.Send(nil, client.nickMaskString, "JOIN", channel.name)
+			}
+
+			//TODO(dan): send priv modes
+		}
+
+		channel.stateMutex.Unlock()
+	}
+
+	server.clients.byNick[oldnick] = client
+
+	oldClient.destroy()
+}
+
 // IdleTime returns how long this client's been idle.
 func (client *Client) IdleTime() time.Duration {
 	client.stateMutex.RLock()
 }
 
 // destroy gets rid of a client, removes them from server lists etc.
-func (client *Client) destroy() {
+func (client *Client) destroy(beingResumed bool) {
 	// allow destroy() to execute at most once
 	client.stateMutex.Lock()
 	isDestroyed := client.isDestroyed
 		return
 	}
 
-	client.server.logger.Debug("quit", fmt.Sprintf("%s is no longer on the server", client.nick))
+	if beingResumed {
+		client.server.logger.Debug("quit", fmt.Sprintf("%s is being resumed", client.nick))
+	} else {
+		client.server.logger.Debug("quit", fmt.Sprintf("%s is no longer on the server", client.nick))
+	}
 
 	// send quit/error message to client if they haven't been sent already
 	client.Quit("Connection closed")
 
-	client.server.whoWas.Append(client)
 	friends := client.Friends()
 	friends.Remove(client)
+	if !beingResumed {
+		client.server.whoWas.Append(client)
+	}
 
 	// remove from connection limits
 	ipaddr := client.IP()
 
 	// clean up channels
 	for _, channel := range client.Channels() {
-		channel.Quit(client)
+		if !beingResumed {
+			channel.Quit(client)
+		}
 		for _, member := range channel.Members() {
 			friends.Add(member)
 		}
 	}
 
 	// clean up server
-	client.server.clients.Remove(client)
+	if !beingResumed {
+		client.server.clients.Remove(client)
+	}
 
 	// clean up self
 	if client.idletimer != nil {
 	client.socket.Close()
 
 	// send quit messages to friends
-	for friend := range friends {
-		if client.quitMessage == "" {
-			client.quitMessage = "Exited"
+	if !beingResumed {
+		for friend := range friends {
+			if client.quitMessage == "" {
+				client.quitMessage = "Exited"
+			}
+			friend.Send(nil, client.nickMaskString, "QUIT", client.quitMessage)
 		}
-		friend.Send(nil, client.nickMaskString, "QUIT", client.quitMessage)
 	}
 	if !client.exitedSnomaskSent {
-		client.server.snomasks.Send(sno.LocalQuits, fmt.Sprintf(ircfmt.Unescape("%s$r exited the network"), client.nick))
+		if beingResumed {
+			client.server.snomasks.Send(sno.LocalQuits, fmt.Sprintf(ircfmt.Unescape("%s$r is resuming their connection, old client has been destroyed"), client.nick))
+		} else {
+			client.server.snomasks.Send(sno.LocalQuits, fmt.Sprintf(ircfmt.Unescape("%s$r exited the network"), client.nick))
+		}
 	}
 }
 

irc/commands.go

 		handler:   renameHandler,
 		minParams: 2,
 	},
+	"RESUME": {
+		handler:      resumeHandler,
+		usablePreReg: true,
+		minParams:    1,
+	},
 	"SANICK": {
 		handler:   sanickHandler,
 		minParams: 2,

irc/help.go

 		text: `REHASH
 
 Reloads the config file and updates TLS certificates on listeners`,
+	},
+	"resume": {
+		text: `RESUME <oldnick> [timestamp]
+
+Sent before registration has completed, this indicates that the client wants to
+resume their old connection <oldnick>.`,
 	},
 	"time": {
 		text: `TIME [server]

irc/idletimer.go

 	"fmt"
 	"sync"
 	"time"
+
+	"github.com/oragono/oragono/irc/caps"
 )
 
 const (
 	RegisterTimeout = time.Minute
 	// IdleTimeout is how long without traffic before a registered client is considered idle.
 	IdleTimeout = time.Minute + time.Second*30
+	// IdleTimeoutWithResumeCap is how long without traffic before a registered client is considered idle, when they have the resume capability.
+	IdleTimeoutWithResumeCap = time.Minute*2 + time.Second*30
 	// QuitTimeout is how long without traffic before an idle client is disconnected
 	QuitTimeout = time.Minute
 )
 	sync.Mutex // tier 1
 
 	// immutable after construction
-	registerTimeout time.Duration
-	idleTimeout     time.Duration
-	quitTimeout     time.Duration
-	client          *Client
+	registerTimeout       time.Duration
+	idleTimeout           time.Duration
+	idleTimeoutWithResume time.Duration
+	quitTimeout           time.Duration
+	client                *Client
 
 	// mutable
 	state TimerState
 // NewIdleTimer sets up a new IdleTimer using constant timeouts.
 func NewIdleTimer(client *Client) *IdleTimer {
 	it := IdleTimer{
-		registerTimeout: RegisterTimeout,
-		idleTimeout:     IdleTimeout,
-		quitTimeout:     QuitTimeout,
-		client:          client,
+		registerTimeout:       RegisterTimeout,
+		idleTimeout:           IdleTimeout,
+		idleTimeoutWithResume: IdleTimeoutWithResumeCap,
+		quitTimeout:           QuitTimeout,
+		client:                client,
 	}
 	return &it
 }
 	case TimerUnregistered:
 		nextTimeout = it.registerTimeout
 	case TimerActive:
-		nextTimeout = it.idleTimeout
+		// if they have the resume cap, wait longer before pinging them out
+		// to give them a chance to resume their connection
+		if it.client.capabilities.Has(caps.Resume) {
+			nextTimeout = it.idleTimeoutWithResume
+		} else {
+			nextTimeout = it.idleTimeout
+		}
 	case TimerIdle:
 		nextTimeout = it.quitTimeout
 	case TimerDead:

irc/numerics.go

 	ERR_REG_INVALID_CALLBACK        = "929"
 	ERR_TOOMANYLANGUAGES            = "981"
 	ERR_NOLANGUAGE                  = "982"
+
+	// draft numerics
+	ERR_CANNOT_RESUME = "999"
 )

irc/server.go

 	return false
 }
 
+// ResumeDetails are the details that we use to resume connections.
+type ResumeDetails struct {
+	OldNick   string
+	Timestamp *time.Time
+}
+
+// RESUME <oldnick> [timestamp]
+func resumeHandler(server *Server, client *Client, msg ircmsg.IrcMessage) bool {
+	oldnick := msg.Params[0]
+
+	if strings.Contains(oldnick, " ") {
+		client.Send(nil, server.name, ERR_CANNOT_RESUME, "*", "Cannot resume connection, old nickname contains spaces")
+		return false
+	}
+
+	if client.Registered() {
+		client.Send(nil, server.name, ERR_CANNOT_RESUME, oldnick, "Cannot resume connection, connection registration has already been completed")
+		return false
+	}
+
+	var timestamp *time.Time
+	if 1 < len(msg.Params) {
+		timestamp, err := time.Parse("2006-01-02T15:04:05.999Z", msg.Params[1])
+		if err != nil {
+			client.Send(nil, server.name, ERR_CANNOT_RESUME, oldnick, "Timestamp is not in 2006-01-02T15:04:05.999Z format, ignoring it")
+		}
+	}
+
+	client.resumeDetails = ResumeDetails{
+		OldNick:   oldnick,
+		Timestamp: timestamp,
+	}
+
+	return true
+}
+
 // USERHOST <nickname> [<nickname> <nickname> ...]
 func userhostHandler(server *Server, client *Client, msg ircmsg.IrcMessage) bool {
 	returnedNicks := make(map[string]bool)